On the concept of a normal metal hot-electron microbolometer for space applications

We present a theoretical analysis and experimental evaluation of a hot-elec tron microbolometer with normal metal absorber for ultrasensitive detecting infrared and submillimeter waves. The basic version of the antenna coupled microbolometer makes use of a hot-electron effect in the thin film resisti ve strip and Andreev reflection of hot electrons at SN interface between th e strip and superconducting antenna. A value of NEP = 5.10(-18) W/Hz(1/2) f or the thermal fluctuation noise and the thermal time constant t = 0.2 mu s at 300 mK have been estimated for one of the realized devices with thermal conductance G approximate to 6.10(-12) W/K. At 100 mK, the thermal conduct ance has been decreased to G approximate to 7.10(-14) W/K, that gives estim ations for the thermal NEP=2.10(-19) W/Hz(1/2) and the time constant t = 5 mu s. An advanced version of the microbolometer includes also additional SI N junctions connected to the resistive strip for electronic cooling the abs orber Such microbolometer is intended as a detector of millimeter and submi llimeter wave radiation for space applications.